Spark discharge pulsing circuit



Oct. 23, 1951 A. E. YOUNG SPARK DISCHARGE PULSING CIRCUIT Filed Sept. 29, 1950 INVENTOR.

Patented Get. 23, 1951 2,572,087 SPARK DISCHARGE PULSING CIRCUIT Allen Earl Young, Lakewood, Ohio Application September 29, 1950, Serial No. 187,648

Claims. (Cl. 315230) (Granted under the act of March 3, 188 3, as

amended April .30, 1928; 370 0. G. 757) This invention relates to spark discharge apparatus and more particularly to a spark discharge pulsing circuit.

Prior art discharge circuits for producing a short duration spark are characterized by a number of limitations and disadvantages. One such prior art device employs a series discharge circuit witha thyratron for triggering, such for example as that disclosed in the patent to Slack et al. for Short Exposure X-Ray Apparatus, No. 2,420,845, issued May 20, 1947. In such a circuit the total energy of discharge must pass through the trigger tube resulting in severe service on the tube and loss of energy.

"Another prior art device employs an auxiliary spark gap for triggering, and is characterized by similar disadvantages.

A- third prior art device employs a main gap having a trigger electrode; the disadvantages of this device are that the gap is subject to high potential at all times, and any leakage between electrodes causes reduction in the charge on the capacitor. Also, the trigger may have undesirable effects on the character of the discharge, and a high voltage trigger source is required.

The apparatus embodying the instant invention overcomes the aforementioned limitations and disadvantages by the use of a circuit in which a thyratron and inductor are serially connected in parallel with two charged capacitors, such that firing the thyratron produces an oscillatory discharge thereby charging one of said capacitors in an opposite polarity and initiating a discharge across a gap connected to corresponding terminals of said capacitors, the initiating potential being built up across the gap by a resistor in the charging lead of the other of the capacitors and connected in parallel with the gap.

Accordingly, it is a primary object of the invention to provide new and improved spark discharge apparatus.

Another object is to provide new and improved apparatus for providing a short duration light source.

Another object is to provide a new and improved short duration light source having a thyratron control.

Other objects and advantages Will become apparent after a consideration of the following specification when taken in connection with the accompanying drawing, in which the single figure thereof comprises a schematic electrical circuit diagram of apparatus embodying the invention.

Particular reference is made now to the drawing for a more complete understanding of the 2 invention. A suitable source of A.-C. potential In is connected by way of fuse l6, leads I4 and I9, time delay contacts H, and switch NJ, to a variable inductor device 2l, commonly known in the trade as a variac, for adjusting the voltage on primary 24 of a high Voltage transformer. Voltage adjustor 2| may have a suitable pilot lamp 20 connected thereacross for indicating when potential is applied thereto. Also connected to the aforementioned source In by way of leads l4 and I9 and switch H is a time delay motor I2 which may be of conventional design and connected to contacts I! for operating the same, and having pilot lamp [3 connected in shunt therewith, the motor also having connected in shunt therewith by way of leads l4 and 15 the primaries 3| and 69 of two filament transformers having secondaries 29 and 68 respectively, for purposes to be hereinafter apparent.

Secondary 25 of the aforementioned high voltage transformer has one terminal thereof connected to ground 30 and the other terminal thereof connected to anode 21 of rectifier tube 26, the filament 28 of tube 26 being connected to filament secondary 29 associated with primary 3|, the filament transformer having higher voltage insulation between windings. The filament 28 is also connected by way of lead 32 and resistors 48, 49, 50, 5|, 52, and 53 to ground 30, and the last named resistors 48-53 have capacitors 4l-46 connected in parallel therewith respectively. The resistors may each have a value of 5 megohms and the capacitors may each have a value of 0.01 mfd. The use of the last named capacitors is optional, the function of said capacitors being only to limit or eliminate feedback of transient voltage pulses from the discharge circuit at the moment of discharge.

Filament 28 is also connected by way of lead 32; resistors 54 and 55, which may each have a value of 2 megohms, and inductor 56, which may have a value of 7.6 microhenries, and lead 62, to anode 64 of a gaseous discharge triode tube generally designated by the reference numeral 63. The aforementioned resistors 54 and 55 should be capable of withstanding a voltage surge of twice the peak value of the voltage provided by the high voltage transformer secondary 25, said surge occurring at the moment of discharge.

A capacitor 58, which may have a value of 0.05 mfd., is connected between the junction between resistor 55 and inductor 56 and ground, and has connected in shunt therewith the series connected resistor BI and capacitor 5'1. Capacitor 51 may have a value of 0.05 mid, and resistor 6 3 may have a value of 5 megohms. Across resistor 61 is connected the light producing gap having gap terminals 59 and 66.

The cathode 65 of tube 63 is connected to ground 30, and the filament 67 is connected to secondary 68 of the aforementioned filament transformer having primary 69. The grid 65 of tube 63 is connected by way of resistor 18 to ground 30. Resistor 78 may have a value of 20 kilohms. The junction between grid 65 and resistor I8 is connected by way of capacitor 76, which may have a value of 0.05 mid, capacitor 14, which may have a value of 1.0 mid, and switch 15 to ground 30. Capacitor 16 has connected in shunt therewith the resistor I! which may have a value of 100 kilohms. Across the switch 15 is connected the terminal strip H1 or other means of providing an external switch for remote operation of subject apparatus. Capacitor M has connected in shunt therewith the battery H, which may have a potential of 90 volts, switch 12, and resistor 13 which may have a value of kilohms. The grid circuit of tube 63 comprises an arrangement, the operation of which will be readily understood by those skilled in the art, for controlling the energization of thyratron 63.

It will be understood that preferably the time of the impulse applied to the grid should be related in a predetermined manner to the oscillation time or frequency of the discharge circuit.

In the operation of the above described apparatus, with the thyratron or other gaseous discharge triode 63 not conducting, capacitors 51 and 58 are charged to the same potential and polarity from tube 26 Upon the firing of the thyratron, capacitor 58 discharges quickly through inductance 55, and as a result the polarity across capacitor 58 is reversed. The voltages across the capacitors thereupon add to a value sufiicient to render the gap conducting, and a discharge, takes place across terminals 59 and El].

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope'of the appended claims the invention may be practiced other than as specifically described.

This invention may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. In apparatus of the character disclosed, in combination, source means for obtaining a high D.-C. voltage, a first capacitor connected to said source means and having said voltage applied thereacross, a second capacitor, a resistor, said second capacitor and resistor being connectedin series across said source means, a gap having the terminals thereof connected across said resistor,

an inductor, a normally nonconducting gaseous discharge tube having an anode, grid, and cathode, said inductor and the anode-cathode path of said tube being connected in series across said first capacitor, and means connected to said grid for causing said tube to conduct, said first capacitor and inductor, while the tube is conducting, providing an oscillatory circuit whereby the potential on said first capacitor assumes a momentary polarity opposite from its original polarity, both said capacitors discharging across said gap when the instant algebraic sum of the voltages across the capacitors attains a predetermined value.

2. Apparatus according to claim 1 wherein said means connected to said grid for causing the tube to conduct comprises a source of potential and an R.-C. network for applying a signal of predetermined characteristics to said grid.

3. In apparatus of the character disclosed, in combination, a first capacitor, a series connected resistor and a second capacitor connected in shunt with said first capacitor, gap means connected across said resistor, means connected to said capacitors for charging them with a predetermined D.-C. voltage, discharge means including a normally non-conducting electron discharge tube and an inductor connected in series across said first capacitor, and means connected to said tube for causing the tube to conduct, the conduction of said tube causing said first capacitor to discharge through said tube and inductor and set up an oscillation whereby the voltage across said first capacitor is reversed in polarity, said first and second capacitors discharging across said gap when the algebraic sum of the voltages across them attains a predetermined value.

4. In apparatus of the character disclosed, in combination, a first capacitor, a second capacitor and a resistor connected in series across said first capacitor, gap means connected across said resistor, means connected to said capacitors for charging them with a predetermined D.-C. voltage, normally open circuit means including an inductor connected across said first capacitor, and means connected to said circuit means for closing the circuit thereof, said first capacitor thereupon discharging through said inductor and setting up an oscillation whereby the voltage across said first capacitor is reversed in polarity, said first and second capacitors discharging across said gap when the algebraic sum of the voltages across them attains a predetermined value.

5. Apparatus according to claim 4 wherein said means connected to said capacitors for charging them comprises a high voltage vacuum tube rectifier.

ALLEN EARL YOUNG.

No references cited. 

